Be a Good Neighbor to Cotton: Strip Cut Your Alfalfa Field

In recent days, you might describe field scout Carlos Silva as part Paul Revere and part State Farm insurance agent.

His jingle might sound like this: “Like a good neighbor, Carlos is there” to spread the word to alfalfa growers that the “lygus are coming, the lygus are coming” to a cotton field near you.

Lygus a threat to cotton. (UC IPM photo)

With the first squares emerging on cotton plants across the Valley, it’s time for farmers to start worrying about lygus invading their cotton fields. And these pests could be traveling from a nearby alfalfa field.

Yes, Carlos reports lygus bugs are plentiful in alfalfa fields, one of their favorite habitats. As growers prepare to start the third harvest, or cutting, in the coming week, he is going around reminding them about the importance of leaving strips of uncut alfalfa in the fields, especially where there is cotton growing nearby. The strips will leave a habitat for lygus to stay in and keep them from fleeing to a cotton field, which is not their preferred home.

“I am starting to talk about strip cutting and being a good neighbor,” Carlos says.

Strip cutting wasn’t important during the first two harvests of the season because cotton season had just started. But now the first squares are developing on the cotton plants.

Strip cutting alfalfa helps control lygus in nearby cotton fields.

Indeed, UC IPM reports lygus bugs are a threat to cotton from the earliest squaring through final boll set. The pests pierce squares, which can shrivel, turn brown and drop to the ground. Losing too many squares will trigger vegetative growth in the plants and end up reducing yields.

Here are tips from UC IPM about strip cutting alfalfa to manage lygus:

• Maintain nearby alfalfa fields in a succulent condition.
• Avoid cutting all alfalfa fields in an area within a short time period. Leave an uncut strip or check at each cutting along the border between alfalfa and cotton to slow lygus migration.
• If lygus populations get very high, uncut strips of alfalfa may be treated with an insecticide if needed, but sprays should be avoided where possible to protect beneficials.

For alfalfa growing next to a cotton field, UC IPM recommends:

• Planting a sufficient area with alfalfa, manage for succulent growth, and alternate cutting half of each strip every two weeks.
• Cutting back with a stalk cutter. In a 28-day cycle, many lygus eggs will be inside the cut stems and will die as the stems desiccate.

Carlos says this practice should be followed for alfalfa fields that are within a two mile radius of a cotton field. These bugs can easily travel that far when their habitats are disrupted during harvest.

  

 Speaking of alfalfa, we hope growers caught today’s Alfalfa Pest and Crop Management Field Day at the Scout Hut in Dos Palos. The event featured Dr. Pete Goodell of UC IPM, Fresno County ag specialist William Griffin and pest control advisor and agronomist Francisco Parra.  Those who missed their presentations about the alfalfa aphid outbreak this year, non-fumigant VOC regulations, vertebrate pest control and drip irrigation in alfalfa will be able to catch the talks on YouTube. Check out the Sustainable Cotton Project’s website for details.